U.S. patent number 4,988,399 [Application Number 07/375,528] was granted by the patent office on 1991-01-29 for process for making a three-piece container involving stretch-blow molding, severing and attaching an end panel to the open bottom.
This patent grant is currently assigned to Aluminum Company of America. Invention is credited to Thomas L. Levendusky, Martin J. Watson.
United States Patent |
4,988,399 |
Watson , et al. |
January 29, 1991 |
Process for making a three-piece container involving stretch-blow
molding, severing and attaching an end panel to the open bottom
Abstract
A method of producing a pair of container bodies. A cylindrical,
hollow preform of a thermoplastic polymer material having a
cylindrical body having a sidewall and an opened neck finish on
each longitudinal end of the preform is provided. The preform is
heated to a temperature above the glass transition temperature of
the polymer and below the melting temperature of the polymer, and
is stretched. The preform is stretched longitudinally by applying
force to at least one of the ends, and is stretched transversely by
introducing fluid pressure into the preform sufficient to form a
stretch blown component having a first neck at one end and a second
neck at the other end, and a body portion between the necks. The
stretch blown component is separated transversely through the body
to provide two container bodies, each having a neck finish
corresponding dimensionally with the respective neck finish on the
preform from which the container bodies are stretch-blown. The
container bodies each have an open bottom end spaced longitudinally
from the respective neck. A three-piece, biaxially oriented
container is provided by attaching an end panel to the open bottom
end of the container body and providing a mating closure onto the
neck finish.
Inventors: |
Watson; Martin J. (Murrysville,
PA), Levendusky; Thomas L. (Greensburg, PA) |
Assignee: |
Aluminum Company of America
(Pittsburgh, PA)
|
Family
ID: |
23481232 |
Appl.
No.: |
07/375,528 |
Filed: |
July 5, 1989 |
Current U.S.
Class: |
156/73.5;
264/454; 264/458; 264/521; 264/527; 264/532; 264/535; 264/68;
29/412; 29/512; 425/529 |
Current CPC
Class: |
B29C
49/14 (20130101); B29C 49/4278 (20130101); B29C
2035/0811 (20130101); B29C 2035/0822 (20130101); B29C
2035/0861 (20130101); B29C 2049/0089 (20130101); B29C
2049/4869 (20130101); B29C 2793/009 (20130101); B29K
2067/00 (20130101); B29K 2105/258 (20130101); Y10T
29/49789 (20150115); Y10T 29/4992 (20150115) |
Current International
Class: |
B29C
49/08 (20060101); B29C 49/14 (20060101); B29C
69/00 (20060101); B29C 049/04 (); B29C 049/10 ();
B29C 049/64 () |
Field of
Search: |
;264/25,68,521,527,532,535 ;425/526,527,529 ;156/73.5
;29/412,512 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Modern Plastics, Apr. 1977, "Stretch-Blow Molding", Dan Kelly, pp.
70-72..
|
Primary Examiner: Silbaugh; Jan H.
Assistant Examiner: Timm; Catherine
Attorney, Agent or Firm: O'Rourke, Jr.; William J. Klepac;
Glenn E.
Claims
We claim:
1. A method of producing a pair of container bodies comprising the
steps of:
providing a generally cylindrical, hollow preform of a
thermoplastic polymer material having a cylindrical body comprising
a sidewall and an open neck finish on first and second opposed
longitudinal ends thereof,
heating the preform having finished neck portions to a temperature
above the polymer glass transition temperature and below the
polymer melting temperature wherein during the heating of the
preform the neck finish on both ends of the preform is shielded
from at least a portion of the heating to minimize the heating of
the neck finish portions and thus avoid softening and distortion of
the neck finish portions.
stretching the heated preform longitudinally by applying force to
at least one of the ends in such a manner that the neck finish
portions are not subject to appreciable longitudinal
stretching,
sealing both open neck finish portions, then stretching the heated
preform transversely by introducing fluid pressure therein
sufficient to form a stretch blown component having a first neck at
one end thereof, a second neck at the other longitudinal end
thereof, and a body portion between the necks, and
separating one end portion of the stretch blown component from the
other end portion of the stretch blown component by severing the
stretch blown component transversely through the body portion to
provide two container bodies, each container body having a neck
finish corresponding dimensionally with the respective neck finish
on the preform from which the container bodies are stretch-blown
and an open end spaced longitudinally from said neck.
2. A method as set forth in claim 1 wherein a shoulder is formed in
each end of the stretch blown component by continuing the
transverse stretching of the preform within a mold cavity, said
shoulders connecting the first neck and the second neck to the body
portion.
3. A method as set forth in claim 1 wherein the body portion
comprises a substantially cylindrical sidewall.
4. A method as set forth in claim 1 wherein the preform is provided
by extruding a thermoplastic polymer material into an elongated,
hollow, cylindrical body, cutting the extruded cylinder into
discrete cylinders and providing the neck finish on first and
second opposed longitudinal ends of the discrete cylinder.
5. A method as set forth in claim 4 wherein the neck finish is
provided by forming exterior threads on first and second opposed
longitudinal ends of the cylinder.
6. A method as set forth in claim 4 wherein the opened neck finish
is provided by spin welding cylindrical, hollow neck finish
components to first and second opposed longitudinal ends of a
cylindrical hollow member.
7. A method as set forth in claim 1 wherein each of the separated
container bodies is dimensionally identical to the other.
8. A method as set forth in claim 1 wherein the ratio of the inside
diameter of the neck finish on the preform to the inside diameter
of the cylindrical body of the preform is greater than or equal to
0.75.
9. A method as set forth in claim 1 wherein the ratio of the inside
diameter of the neck finish on the preform to the inside diameter
of the cylindrical body of the preform is about 1.0 to 1.3.
10. A method as set forth in claim 1 wherein the heating of the
preform is accomplished through the use of a method selected from
the group consisting of infrared radiation and radio frequency
heating.
11. A method as set forth in claim 1 wherein at least a portion of
the longitudinal and transverse stretching occur
simultaneously.
12. A method as set forth in claim 1 wherein the majority of the
longitudinal stretching is accomplished by mechanical stretching of
the preform along the longitudinal axis.
13. A method as set forth in claim 1 wherein the longitudinal
stretching precedes the transverse stretching of the preform.
14. A method as set forth in claim 1 wherein the preform is grasped
with clamping means having engaging teeth disposed about a ring
portion of the preform extending outwardly of an outside surface of
the preform and located at a longitudinally inner portion of each
neck, which ring portion extends outwardly of the cylindrical
preform about the circumference of the preform.
15. A method as set forth in claim 14 wherein the longitudinal
stretching is accomplished by moving the clamping means away from
one another at a substantially constant rate.
16. A method as set forth in claim 14 wherein one clamped end of
the preform is held stationary while the other clamped end of the
preform is moved to accomplish the longitudinal stretching.
17. A method as set forth in claim 14 wherein both clamped ends of
the preform are moved away from one another to accomplish the
longitudinal stretching.
18. A method as set forth in claim 1 wherein the preform is
stretched transversely by introducing fluid into the hollow preform
through one end of the preform.
19. A method as set forth in claim 1 wherein the preform is
stretched transversely by introducing fluid into the hollow preform
through both ends of the preform.
20. A method as set forth in claim 1 wherein the fluid is selected
away from the group consisting of air, air with additives, an inert
gas and an air-inert gas mixture.
21. A method as set forth in claim 1 further including the step of
exhausting the fluid pressure from the stretch blown component
after the stretching is completed.
22. A method as set forth in claim 1 further including the step of
providing a mold about the preform against which the component is
formed.
23. A method as set forth in claim 22 wherein the mold is provided
with a substantially cylindrical cavity against which the
cylindrical sidewall of the component is formed.
24. A method as set forth in claim 23 wherein the substantially
cylindrical mold cavity includes a centrally located outwardly
extending circumferential channel about the cylindrical mold cavity
against which an outwardly extending circumferential flange is
formed along the cylindrical sidewall of the component.
25. A method as set forth in claim 24 wherein the stretch-blown
component is separated through the circumferential flange to
provide two container bodies.
26. A method as set forth in claim 25 wherein the open bottom end
of each separated container body is trimmed about a separated
flange portion.
27. A method as set forth in claim 1 wherein the open bottom end of
each separated container body is trimmed to receive an end
panel.
28. A method as set forth in claim 27 wherein the open bottom end
is trimmed prior to subsequent heating and flanging of the open
bottom end of the container body over a flanging tool.
29. A method as set forth in claim 27 further including the step of
seaming an end panel to the open bottom end of the container
body.
30. A method as set forth in claim 29 wherein the end panel seamed
to the hollow bottom end of the container body is substantially
metallic.
31. A method as set forth in claim 29 wherein the end panel seamed
to the bottom end of the container body is a material selected from
the group consisting of aluminum, steel, tinplate, polymer-aluminum
laminate, polymer-steel laminate and PET.
32. A method as set forth in claim 1 wherein the polymer is
provided from a biaxially oriented, crystallizable material.
33. A method as set forth in claim 1 wherein the polymer is a
material selected from the group consisting of polyester and
polyamide.
34. A method as set forth in claim 1 wherein the preform is a
material selected from the group consisting of PET, PEN and
amorphous nylon.
35. A method as set forth in claim 1 wherein the preform is
provided from PET mixed with a pigment.
36. A method as set forth in claim 1 wherein the preform comprises
multiple layers of dissimilar thermoplastic polymer materials.
37. A method as set forth in claim 1 further including the step of
spin welding an end panel to the open bottom end of a container
body, wherein both the end panel and the container body comprise
PET material.
38. A method of producing a pair of containers comprising the steps
of:
providing a generally cylindrical, hollow preform of an extruded
thermoplastic polymer material selected from the group consisting
of PET, PEN and amorphous nylon, said preform having an open neck
finish on first and second opposed longitudinal ends thereof, and
first and second ring portions extending outwardly of the preform
at locations longitudinally inwardly of each neck about the
circumference of the preform,
heating the preform in the area between the finished neck portions
to a temperature above the polymer glass transition temperature and
below the polymer melting temperature wherein during the heating of
the preform, the neck finish on both ends of the preform are
shielded from at least a portion of the heating to minimize the
heating of the neck finish portions and thus avoid softening and
distortion of the neck finish portions.
stretching the heated preform longitudinally by grasping at least
one ring portion and applying force to at least one of the ends in
such a manner that the neck finish portions are not subject to
appreciable longitudinal stretching,
sealing both open neck finish portions, then stretching the preform
transversely by introducing fluid pressure into a hollow chamber of
the preform sufficient to form a stretch blown component having a
first neck at one end thereof, a second neck at the other
longitudinal end thereof, a substantially cylindrical portion
between the necks, and shoulder connecting the first and second
necks to the body portion,
separating one end portion of the stretch blown component from the
other end portion of the stretch blown component by severing the
stretch blown component transversely through the body portion to
provide two container bodies, each container body having a neck
finish corresponding dimensionally with the respective neck finish
on the preform from which the container bodies are stretch-blown
and an open end spaced longitudinally from said neck, and
applying a metallic bottom end panel to close the open end of each
container body to form a pair of containers.
Description
BACKGROUND OF THE INVENTION
The present invention relates to blow molding of thermoplastic
container bodies. More particularly, this invention relates to the
production of three-piece containers formed from tandem container
bodies, blow molded from a hollow, thermoplastic preform having a
neck finish on both ends thereof.
Blow molding of thermoplastics has been taught in the prior art.
This art generally teaches the process as involving the steps of
forming a hollow tube, heating the tube, then introducing a gas
under pressure into the hollow tube. The pressurized gas expands
the heated tube against a mold to form a shaped article. When the
hollow tube is stretched mechanically in the longitudinal direction
either before or during expansion with pressurized gas, the process
is sometimes called stretch-blow molding.
Stretching of a thermoplastic material both longitudinally and
transversely results in a high degree of biaxial orientation of the
molecular structure of the thermoplastic material. Such biaxial
orientation provides favorable properties including high tensile
strength and yield strength, toughness or high resistance to
impact, low creep at low weight to volume ratios and sufficient
barrier properties which render this material useful in containing
liquids under pressure.
Blow molding and stretch-blow molding are taught in the prior art
including U.S. Pat. No. 4,447,199. The simultaneous production of
multiple containers by blow molding a single hollow tube has also
been taught in the prior art, including U.S. Pat. Nos. 3,457,590,
4,103,411 and 4,796,766.
One of the many challenges encountered in a blow molding operation
is the ability to provide a blow molded container body having a
neck finish of close dimensional tolerance onto which a closure is
adapted to be applied. Blow molding threads into a neck finish, for
example, is difficult. In fact, it is often necessary to perform
subsequent neck finishing operations, after blow molding, in order
to obtain or retain the close dimensional requirements of a neck
finish, whether threads, crowns, lugs or otherwise.
Despite significant progress in this art and various alternative
blow molding methods, there is still a need and a demand for
further improvement. Accordingly, a new and improved method is
desired which produces a pair of biaxially oriented container
bodies in a blow molding process having neck portions which do not
require subsequent finishing operations to assure the dimensional
tolerance of the neck finish.
SUMMARY OF THE INVENTION
This invention may be summarized as providing a method of producing
a pair of container bodies comprising the steps of providing a
cylindrical, hollow preform of a thermoplastic polymer material
having a cylindrical body comprising a sidewall and an opened neck
finish on each longitudinal end of the preform. The preform is
heated to a temperature above the glass transition temperature of
the polymer and below the melting temperature of the polymer, and
is stretched. The preform is stretched longitudinally by applying
force to at least one of the ends. The longitudinal stretching can
be accomplished by moving the clamping means away from one another
at a substantially constant rate or holding one clamped end
stationary while moving the other clamped end. The preform is
stretched transversely by introducing fluid pressure into the
preform sufficient to form a stretch blown component having a first
neck at one end and a second neck at the other end, and an integral
body portion between the necks. The stretch blown component is
separated transversely through the body to provide two container
bodies, each having a neck finish corresponding dimensionally with
the respective neck finish on the preform from which the container
bodies are stretch-blown. The container bodies each have an open
bottom end spaced longitudinally from the respective neck. A
three-piece, biaxially oriented container is provided by attaching
an end panel to the open bottom end of the container body and
providing a mating closure onto the neck finish.
Among the advantages of this invention is the provision of a method
of blow molding a pair of biaxially oriented container bodies
having neck portions which require no finishing operations to
maintain their dimensional tolerance, and in which the neck
finishes of the blown containers correspond dimensionally with the
respective neck finishes on the preform from which the containers
are blow molded.
Another advantage of this invention is the provision of a method of
producing biaxially oriented container bodies at increased
production rates, and at lower costs as compared to prior
methods.
A further advantage of the present invention is the provision of a
three-piece container having a biaxially oriented blow molded
thermoplastic body, a base seamed to an open bottom of the body and
a closure applied to a neck finish opposite the open bottom which
container exhibits improved container base stability.
Another objective of this invention is to provide a method of blow
molding a pair of container bodies from an elongated, generally
cylindrical thermoplastic hollow preform having a neck finish on
both longitudinal ends thereof, in which the neck finish is not
subjected to appreciable stretching.
A feature of this invention is that the neck finishes on the
longitudinal ends of the hollow preform correspond dimensionally to
the neck finishes on the respective ends of the pair of containers
which are blow molded from the preform.
These and other advantages and objectives of the invention will be
more thoroughly understood and appreciated with reference to the
following description and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a hollow preform of the present
invention.
FIGS. 2 and 3 are cross-sectional views of alternative hollow
preforms of the present invention.
FIGS. 4-9 are fragmentary cross-sectional views of apparatus for
producing a pair of container bodies, illustrating the production
thereof through the following sequence of steps:
FIG. 4 - feeding of the preform,
FIG. 5 - heating of the preform,
FIG. 6 - aligning a gripper and a mold,
FIG. 7 - closing the gripper and the mold,
FIG. 8 - stretch-blow molding of the preform, and
FIG. 9 - ejecting the blown component.
FIG. 10 is an enlarged cross-sectional view of a gripper used in
the present invention.
FIG. 11 is a cross-sectional view of a container body separated
from the component shown in FIG. 9.
FIG. 12 is a cross-sectional view of a container body as shown in
FIG. 11 after the peripheral edge around the open bottom of the
container body has been flanged to receive an end panel.
FIG. 13 is a cross-sectional view of an illustrative three-piece
container of the present invention having a container body as shown
in FIG. 12 with an end panel seamed to enclose the open bottom, and
a closure mating with the finished neck of the container body.
DETAILED DESCRIPTION
Referring particularly to the drawings, FIG. 1 illustrates a
typical preform 10. The preform 10 is a generally cylindrical
hollow body of a thermoplastic polymer material. Although a
preferred thermoplastic polymer material for the preform is
polyethylene terephthalate also called PET, other polyester and
polyamide materials including, but not limited to,
poly(ethylene-2,-6 naphthalate) also called PEN, and amorphous
nylon are comprehended for the preform of the present invention. It
will be appreciated by those skilled in the art that the
thermoplastic polymer material of the present invention may include
minor amounts, such as less than 10 mole percent, of a comonomer
and minor amounts of additives such as stabilizers, antioxidants,
ultraviolet light screening agents, dyes or pigments. Also, the
preform and the resultant components may comprise multiple layers
of dissimilar thermoplastic polymer materials, which may be used to
improve barrier properties, i.e., resistance to oxygen
permeability.
The hollow preform of this invention may be made by a number of
techniques. For example, the preform may be provided by extruding a
thermoplastic polymer material into an elongated, hollow,
cylindrical tube. The extruded tube, or cylinder, may be cut into a
number of discrete cylinders. The discrete cylinders may then be
provided with a neck finish on both ends thereof. Another method of
making the preform is to injection mold a thermoplastic polymer
material. With appropriate molds and polymer materials, the preform
may be injection molded with the neck finish on both opposed
longitudinal ends of the injection molded cylinder, in the as
molded condition, or the injection molded article may have a neck
finish subsequently provided on both ends of the preform. The neck
finish may be provided by spin welding cylindrical, hollow neck
finish components to the opposed ends of a cylinder.
Regardless of the method used to provide the preform, the preform
10 has a substantially cylindrical body 12 and a hollow chamber 14
extending axially through the body 12. At each opposed longitudinal
end of the cylindrical body are necks, namely a first neck portion
16 and a second neck portion 18. The neck portions are finished
prior to the blow molding operation described in detail below. It
will be appreciated by those skilled in the art that finished neck
portions include those necks which require substantially no working
to receive a mating closure thereon. Finished necks comprehend
threaded portions, crowned portions, lugs or other structures
adapted to accept a mating closure to seal the component about the
neck.
In a preferred embodiment as illustrated in FIG. 1, the inside
diameter d.sub.2 of the cylindrical body portion 12 of the preform
10 is substantially uniform along the length of the body portion
12. In this development, the inside diameter d.sub.1 of the neck
portion 16 or 18 is also substantially uniform along the length of
the neck portion. Preferably, the inside diameter d.sub.1 of the
neck portion 16 or 18 is larger than the inside diameter d.sub.2 of
the cylindrical body 12, and in a preferred embodiment the ratio of
d.sub.1 to d.sub.2 is greater than or equal to 0.75, and more
preferably this ratio is from about 1.0 to about 1.3.
The preform 10 shown in the drawing also includes a ring 20 around
the preform at a location near the base of the first neck portion
16, and another ring 22 around the preform at a location near the
base of the second neck portion 18. The ring 20 or 22, which may or
may not be circumferentially continuous, provides a location where
the end portions of the preform may be held or gripped or stretched
during a blow molding or stretch blow molding process as will be
explained in more detail below.
The preform 10, illustrated in FIG. 1, has first and second neck
portions 16 and 18 which are dimensionally identical to one
another. This structure may be preferred, for example, where the
two container bodies being formed from the preform are intended to
be dimensionally identical. It will be appreciated that where the
pair of container bodies being formed are dimensionally identical,
production rates may be increased. Further, after severing the
blown component into two identical container bodies, there is no
requirement that such container bodies be segregated in subsequent
manufacturing, material handling, and processing operations.
In FIG. 2 is shown a preform 24 similar to the preform 10 shown in
FIG. 1 in that the inside diameter of the body portion is
substantially uniform. However, the first finished neck portion 26
is not the same, dimensionally, as the second finished neck portion
28. The first neck portion 26 has a larger diameter than the second
neck portion 28 even though both are provided with a threaded
finish. It will be appreciated that the finished necks provided at
opposed longitudinal ends of the preform may have different types
of finishes, in addition to having different dimensions. In these
instances, the blow molding process will be directed to producing
two different container bodies when the blown component is
separated into two container bodies.
FIG. 3 illustrates an alternative preform 30 of the present
invention. This preform 30 has a generally cylindrical, hollow body
portion 32 and first and second neck portions 34 and 36 on the
longitudinal ends of the body 32. The finished neck portions
include a crown finish 38 as opposed to the threaded finish shown
in FIGS. 1 and 2. It will be understood by those skilled in the art
that any type of container finish may be provided on the preform of
the present invention, provided that such neck portions do not
require subsequent forming after the blow molding operation.
FIGS. 4 through 9 illustrate fragmentary cross-sectional views of
apparatus for producing a pair of container bodies in accordance
with the present invention. FIG. 4 shows a preform 10 positioned on
a support collet 40, extending upwardly of a base 42. The base 42
has a shoulder 44 on which the outer face 46 of one of the necks 16
of the preform 10 sits. The preform 10 should fit easily over the
support collet 40 with little or no interference therebetween.
After the preform 10 has been positioned as shown in FIG. 4, the
preform is heated, such as by the induction heating coils 48 shown
in FIG. 5. Infrared radiation and radio frequency (rf) heating are
also adequate methods of heating the preform. In a preferred
embodiment shields 50 and 52 are provided around the finished neck
portions 16 and 18, respectively, to minimize the heating of the
finished neck portions of the preform and thus avoid softening and
distortion of the neck. The part of the preform that is to be
stretch blow molded is heated to a temperature above the glass
transition temperature of the polymer, and below the melting
temperature of the polymer. It has been found that for polyethylene
terephthalate material heating the preform to a temperature on the
order of about 90.degree. C. to 105.degree. C. is adequate to
exceed the glass transition temperature yet avoid exceeding the
melting temperature or inducing crystallinity (whitening) in the
preform.
After the preform 10 is heated, the preform is disposed inside a
mold, such as mold 54 shown in FIG. 6. The mold restricts the
outward deformation of the preform during the blow molding process.
The preform is positioned on the support collet 40 along the
central axis of the mold. Substantially simultaneously with the
disposition within the mold 54, the upper neck 18 of the preform is
gripped. Preferably, the preform 10 is gripped at the ring 22
around the neck portion 18, with a suitable gripping device 56.
With the first neck portion 16 held firmly at the base 42 of the
support collet 40, the gripping device 56 is moved along the
central axis of the mold in a direction away from the opposing neck
portion to axially stretch the preform. During stretching, fluid
pressure, such as with air, is introduced into the hollow chamber
14 of the preform 10. The fluid pressure is sufficient to stretch
the preform transversely. Such transverse and axial stretching of
the preform 10 is accomplished while the preform retains heat
between the glass transition temperature and the melting
temperature of the preform material.
The stretch blown component formed by this process has a first neck
16 at one end and a second neck 18 at the other longitudinal end,
and a body 58 therebetween. The body 58 of the stretch blown
component conforms dimensionally with the dimensions of the inside
wall 60 of the mold 54.
FIG. 10 shows an enlarged cross-sectional view of a gripping device
56 of the present invention. The device 56 includes jaws 62 having
a first ledge 64 which, when closed, engages the ring 22 around one
neck 18 of the preform, and a second ledge 66 which restricts the
axial movement of the gripper 56 at the point where the second
ledge 66 engages a projecting step 68 on the closed mold 54. A
generous lead-in chamfer on the ring 22 insures proper seating of
the preform and prevents a clash in the event that a preform is not
fed properly. As shown in FIG. 10, the closed gripper jaws 62 clamp
the top finish of the neck against a sealing member 70 in suitable
fashion to create an air tight seal against the top edge of the
preform. In a preferred embodiment, four equally spaced jaws 62 are
provided on the gripping device 56.
FIG. 7 shows the gripping device 56 engaged about the ring 22 on
the upper neck 18 of the preform 10, while the lower neck 16 is
held by the closed mold 54 on the base 42. The preform 10 is
clamped, sealed and in a properly heated state for the stretch-blow
operation.
Axial stretch of the preform is accomplished by axial movement of
the gripping device 56 from the position shown in FIG. 7 to the
position shown in FIG. 8. Radial stretch is accomplished by
introducing fluid pressure into the hollow chamber 14 of the heated
preform 10. The fluid may be air, air with additives, an inert gas
or an air-inert gas mixture. In a preferred embodiment, fluid
pressure is provided by blowing air into the sealed preform 10. Air
may be introduced through one or both ends of the preform. In one
embodiment air is fed through the base 42 and simultaneously
through a central passage 72 in the sealing portion of the gripping
device 56, as shown in FIG. 10. The gripping device 56 moves during
the stretch-blow process until the second ledge 66 of the jaw 62
bottoms against the projecting step 68 on the mold.
As shown in FIG. 8, a stretch blown component is formed by the
stretch blow process. The component has a substantially cylindrical
body and an open neck finish on both ends. The neck finish 16 and
18 on both ends of the blown component correspond dimensionally
with the respective neck finish on the preform 10 from which the
component is stretch blown. In a preferred embodiment as
illustrated in FIG. 8, an outwardly extending circumferential
flange 74 is blown into the substantially cylindrical sidewall 76
of the component. The flange 74 is centrally located in the
sidewall 76, and provides a location where the component may be
divided to form the body of a three-piece biaxially oriented
container of this invention, as explained below.
After the component has been stretch blow molded, as shown in FIG.
8, it is appropriate to exhaust the fluid pressure from inside the
component. This may be accomplished by opening the mold 54 and then
releasing the gripping device 56 and thereby breaking the air tight
seal against the upper neck 18. The component may then be
transferred to an appropriate removal station.
The component comprises two container bodies integrally joined
base-to-base at the circumferential flange 74. The component is
separated by cutting through the circumferential flange 74. After
cutting, each container body 78, as shown in FIG. 11, has an open
neck finish 18 and an unfinished open bottom end portion 80. To
form the three-piece biaxially oriented container of the present
invention, an end panel 82 is applied, such as by double seaming,
to the open bottom end portion 80, and a mating closure, such as a
threaded closure 84 shown in FIG. 13, is applied to the neck
portion 18. To apply the end panel 82 to the bottom end portion 80
of the polymer container body 78, the bottom edge 86 of the
container body may have to be cut and/or trimmed. It may be
possible to provide an in-mold trimming system to enable ejection
from the stretch blown mold of already trimmed container bodies 78.
In any event, the bottom edge 86 typically requires trimming, such
as to the shape generally shown in FIG. 12, to receive an end panel
82 in a double seaming operation, with adequate body/end panel
overlap within the seam. It will be appreciated that the component
may be stretch blown into a variety of configurations, and may be
blown without a circumferential flange 74. Such containers may be
cut, then the bottom edge 86 may be forged over a flanging tool, or
the like, to create a trimmed edge or seamable flange such as the
edge 86 shown in FIG. 12. To provide a double seam of an end panel,
such as an aluminum end panel, to a PET container body, standard
chucks and rolls may be used on standard seamers at operating
speeds which are known in the art. In addition to aluminum, the end
panel may be made of steel, tinplate, polymer-aluminum laminate,
polymer-steel laminate or a polymer such as polyethylene
terephthalate. In certain seaming operations, the container body
may have to be pressurized to provide an adequate top load for
seaming. For certain applications, end panels may be snapped onto a
trimmed bottom edge of the container body. Such applications
include dry, rather than liquid, storage and non-pressurized
applications. When both the end panel and the container are made of
PET, end panels may be spin welded to the open bottom end of the
container body.
The three-piece container of the present invention is characterized
by a bottom end panel 82 which provides rigidity and base stability
for the container, as opposed to a container having an integral
bottom resulting from the blow-molding process. Additionally, the
provision of the finished neck portions 16 and 18 on the preform 10
prior to the stretch blow process, which retain their dimensional
integrity through the process, eliminates the need for subsequent
neck finishing operations after the component is blow molded.
Furthermore, the method of the present invention provides a tandem
component, which when separated into two container bodies, results
in little or no scrap in the process, which needs to be recovered,
processed or discarded. The present process also results in
increased output rates and thus reduced unit production costs, even
considering the material costs of the end panel. Finally, the
process of this invention produces a three-piece container having
increased shelf life through a reduced surface area to volume
ratio, and such container having a polymer body and a metallic end
provides a container with higher barrier properties.
What is believed to be the best mode of this invention has been
described above. It will be apparent to those skilled in the art
that numerous variations of the illustrated and described details
may be made without departing from the scope of this invention.
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